Maintenance of a marmoset breeding colony for production of marmosets for viral oncology studies. This includes: Determination of the biological properties of the Epstein-Barr virus (EBV); Delineation of the pathotenesis, immunology, and host cell-virus relationships of HVS; HVS-2 transformation of marmoset cells in vitro and oncogenicity of transformed cells in autologous and homologous hosts; Studies of CMV transformation of simian and human lymphocytes in vitro and experimental infection of marmosets; Demonstration of the in vivo interaction between EBV and SSV-1/SSAV-1 or GAOV, with in vitro and biochemical studies as follow-up for the in vivo demonstration; and Determination of the response of marmosets to virus preparations suspected to be involved in oncogenesis in humans.